Speed responsive propeller pitch controller



March 6, 1951 R. H. BRANDES SPEED RESPONSIVE PROPELLER PITCH CONTROLLER Filed April 10, 1948 9 Sheets-Sheet 1 INVENTOR.

R. H. BRANDES SPEED RESPONSIVE PROPELLER PITCH CONTROLLER March 6, 1951 9 Sheets-Sheet 2 Filed April 10, 1948 IN V EN TOR.

March 6, 1951' R. H. BRANDES SPEED RESPONSIVE PROPELLER PITCH CONTROLLER Filed April 10, 1948 m? 9 Sheets-Sheet 3 IN VEN TOR.

March 6, 1951 R. H. BRANDES SPEED RESPONSIVE PROPELLER PITCH CONTROLLER Filed April 10, 1948 9 Sheets-Sheet 4 INVENTOR. By W March 6, 1951 R. H. BRANDES SPEED RESPONSIVE PROPELLER PITCH CONTROLLER 9 Sheets-Sheet 5 Filed April 10, 1948 G l-k 4/ 6 22 M I I w V /40 I /65 M3 327 r 84 li 4 INVENTOR.

- aPEE551/EE g Rsqouzrae 7514. BY f Y ZZWZZ March 5 1951 R. H. BRANDES SPEED RESPONSIVE PROPELLER PITCH CONTROLLER Filed April 10, 1948 9 Sheets-Sheet 7 0 I an 1 I INVENTOR. ,4 EM

FOE VALVE u/v& 50 233 March 6, 1951 BRANDES 2,544,131

SPEED RESPONSIVE PROPELLER PITCH CONTROLLER Filed April 10, 1948 9 Sheets-Sheet 8 March 6, 1951 BRANDES 2,544,131

SPEED RESPONSIVE PROPELLER PITCH CONTROLLER Filed April 10, 1948 9 Sheets-Sheet 9 1N VEN TOR.

moi/174M 7 Patented Mar. 6, 1951 SPEED :RESPONS IVE PROPELLER PITCH CQNTROLLER Roy H. Brandes, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application April 10, 1948, Serial No. 20,282

Claims. 1

This invention relates to stabilized control of propeller blade angle for .the purpose of governing the speed of the engine which drives the propeller, and more particularly to a controller .comprising a blade angle controlling hydraulic servo having a cylinder, a piston therein and a rod connected with the piston and extending through one end of :the cylinder and connectible with blade angle changing mechanism, .a fluid reservoir, a pump connected with the reservoir for supplying fluid under pressure, means connecting the pump with the rod end of the servo-cylinder, a 'flyweight governor, means for-driving the pump and governor, a stabilizer cylinder, a piston therein, a rod extending from the piston through one end of said cylinder, a lever connected with saidl stabilizer piston rod, a fulcrum for said lever, a duct connecting one end .of the stabilizer cylinder with the head end of the servocylinder, means for controlling admission of pressure fluid from the pump .to the other end of the stabilizer cylinder or the draining thereof and comprising a, valve connected with the governor and a follow-up valve operatedby the lever, means for controlling admission of pressure fluid from the pump to the head end of servo-cylinder or the draining thereof and comprising a third valve and a second lever operated by the first lever for operating said third valve and a fulcrum for the second lever.

An object of this invention is to provide for adjustment ofthe fulcrum of the levers of the controller for various purposes, namely, to eifect longitudinal adjustment ofthe follow-up valve so that flow of fluid into or out of one end of the stabilizer cylinder will "be blocked when the governor is on speed, to control the degree of sensitivity of the controller to rate of change of speed error and to control the degree of sensitivity of the controller to the amount of speed error.

An object of the invention is to provide either for slow or for rapid action of the controller in response to the setting of an action-selecting member under control by the pilot.

A further object is to provide means operated by the controller for controlling electrical circuits which cause operation of devices which indicate to the pilot the existence of overspeed or unders-peed which the controller can correct either slowly or rapidly as the pilot may choose by operation of the action-selecting means.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view of one side of the controller.

Fig. 2 is a view of the opposite side of the controller.

Fig. 2A is a sectional view on line 2A2A .of Fig. 1'7.

Fig. 3 is a sectional view on line 33 of Fig. 1.

Fig. 4 is a fragmentary view in the direction .of arrow 4 of Fig. 3.

Fig. 4A is a sectional view on .line 4A4A of Fig. 4.

Fig. 5 is a sectional view on line 5-5 of Fig. 4.

Figs. 6 and 7 are sectional views on lines li6 and '|l respectively of Fig. 3 with valve parts .removed.

Fig. 811s a sectional view on line 3'8 of Fig. 5 with valve part removed.

Fig. 9 is a top view of the controller.

Fig. 10 is a bottom View of the supporting bracket of the controller.

Fig. .11 is a top view with the top cover removed.

Figs. 12 and 13 are sectional views on lines l2--I2 and l3-l3 respectively of Fig. 11.

Fig. 14 is a diagrammatic composite of various sectional views included in Figs. 13 and 15.

Fig. '15 is a sectional view on line 15-15 of Fig. .11.

Fig. 16 is a fragmentary view in the direction of arrow I6 of Fig. 15.

Fig. 17 is a bottom view with the bottom bracket removed, the part in section being on line l'l-H of Fig. '15.

Figs. 18 and 19 are sectional views respectively on lines l"8l8 and l9l9 of Fig. .17.

Figs. 20, 21 and 22 are respectively sectional views on lines '202B, 2l--2l .and 22-22 of the housing 3| inFig. .15.

Fig. 23 is a diagram of the controller.

Referreing to Figs. 11 and 15.. a base bracket supports and provides the bottom cover for a housing 3| having a partition 32 and closed at the top by a cover 33.. Partition 32 supports a bushing 34 for a shaft 35 driven by the engine through a gear 36 and driving a gear 31. The hole 38 .in the bracket 30 is sealed by ring 39 attached by screws 40 to bracket 30 and having an annular flange 4] engaged by a rotary seal ring 42 driven by the shaft .35 through member 43 pinned thereto and urged against flange l-I by a spring 44 pressing against a washer 35 engaging the bushing 3%.

Gear 31 meshes with gear (also Fig. 11) integral with a plate I which is connected by leaf Spring hinges 52 with weights 53 enclosed by a guard 54 attached to plate 5I. Weights 53 are connected by a flexible stirrup 55 with a disc 56 surrounding a valve 80 which extends also through a member 51, the stirrup 55, the inner race of ball bearing 58, a spring cup 59, all these parts being retained in assembly by a nut 60 threaded on the upper end of valve 80.

Spring BI is confined under compression between cup 59 and a cup 62 which pin 63 attaches to a lever 64 fulcrumed on pins 65 extending from a nut 65 threaded on a screw 61 having a radially serrated flange 68 engageable with similar serrations of a plate 69 retained by cover 33 on the housing 3|. By removing screws and cover 1 I, access is had to the head of screw 61. By applying a screwdriver thereto, the screw 61 can be turned to change the Vertical location of the nut 66. As the screw 61 is turned, it is cammed down by virtue of the serrations of its flange and of the plate 69 and then moves back under the action of spring 6I to fully reengage the serrations which hold the screw in a required position for initial adjustment of the compression of spring 6|.

The speed setting of the controller is effected by movement of lever 64 about its fulcrum pins 65, said movement being effected by the pilot who manually operates a lever 12 attached to a shaft 13 which is connected with a cam lever 14 which engages the lever 64. Nut retains the lever 14 on the shaft 13. Shaft 13 is journaled in a bushing 16 supported by the housing 3I and its movement is limited by engagement of lever 12 with stops 11b (Fig. l) of a plate 11 which screws 18 attach to housing 3 I.

Valve 80 has a land 8| which controls ports 82 connecting with a groove 83 of a sleeve valve 84 which is movable in a valve guide 85 having ports 81 connecting groove 83 of valve 84 with its own port 81. Guide 85 has a groove 88 which ports 89 connect with a groove 90 of valve 84 and ports 9| connect the groove 90 with the interior of valve 84. A C-washer 93 is received by a groove of guide 85 which together with a washer 94 is received by a pocket in partition 32. These washers and guide 85 are retained by a plate 95 which screws 96 attach to the partition 32. Guide 85 supports seal rings 92.

The open lower end of valve 84 (Fig. 15) has a drain opening which receives a leaf spring I00 attached to a plate IOI. Spring I00 urges the valve 84 against the plate IOI and a spring to be described urges the plate IOI against a disc I02 having a notch I03 which receives a pin I04 carried by a nut I05 threaded on a screw I06 having a slotted head I 01 (Fig. 2) received by a pocket in the flange I08 of a bushing I09 rotatably supported by the housing 3|. The hole in the bushing I09 which receives the nut I05 is eccentric to the axis of rotation of the bushing.

Before making adjustments of the screw I06 and bushing I09, a cover IIO attached to the housing 3| by screws MM is removed. When the bushing I09 is turned, the screw I06 and nut I05 are bodily adjusted vertically as viewed in Fig. 15 for the purpose of vertically adjusting the sleeve valve 84 so that its ports 82 will be blocked by the land 8| of valve 80 when the engine which drives the governor is on speed. To retain the bushing I09 in the desired position of adjustment, its flange I08 has notches I08a Fig. 15) differing in number by one from the number o holes I080 (Fig. 2A) in the housing 3| One of the notches I08a will be located in alignment with or relative close to alignment with a hole I 08c. If not exactly in alignment, the bushing I09 can be turned to bring the nearly aligned notch I08a into exact alignment with that hole I080 without causing ports 82 of valve 84 to be unblocked by valve land 8I. Then the pin I081) (Figs. 2A and 17) is pushed through the aligned notch and hole.

When the pin I04 is in the position shown in Fig. 15 and disc I02 is moved about the pin I04 as a fulcrum by means to be described, substantially no movement of the valve 84 can take place. By turning the screw head I01 clockwise (Fig. 2) the pin I04 is initially adjusted to the left of the position shown in Fig. 15 into a position such that movement of disc I02 about the fulcrum pin I04 will effect the required amount of movement of valve 84. When the pin I04 is in the desired position of adjustment, the cover IIO is attached to the housing 3I in order to press the screw head I01 against a friction washer I01a which prevents rotation of the screw I06 and in order to retain the pin I 08b.

The purpose of the adjustment stated in the preceding paragraph is to locate, in a required relation to valve 84, the fulcrum of a lever I I5 of which the disc I 02 is a part. Lever I I5 is connected by pin H6 with a rod II1 connected to a piston H8 in a cylinder II9 which a cover I20 retains in a pocket provided by the housing. As will be explained later, piston II 8 moves when there is a speed change which causes valve to move its land 8I out of alignment with ports 82 of valve 84, and piston II8 moves in a direction to cause valve 84 to follow up valve 80 until ports 82 are closed by valve land 8|. The location of pin I04 determines how much movement of piston II 8 is required to bring valve 84 into port blocking position. The greater the movement required of piston H8 to bring valve 84 into port blocking position relative to valve 80, the lesser will be the sensitivity of the governor to acceleration or rate of change of speed error. Cover I20 provides a guide I2I for the free end of lever 64. The upper end of the cylinder H9 is connected with hydraulic circuits by a duct to be described in the cover. The lower end of cylinder H9 is connected with hydraulic circuits by holes I22 and annular groove I23 in the cylinder.

Referring to Fig. 13, the partition 32 receives a valve guide I30 retained by a plate I3I which a screw I32 attaches to the partition. Guide I30 has grooves I33 and I35 which ports I34 and I36 respectively connect with the interior of the guide. Guide I30 supports seal rings I31 and receives a pin I38 which retains a spring I39 which urges downward a valve I40 having a land I4I which controls ports I36 of guide I30. The lower end of valve I40 engages a pad I42 of a screw I43 threaded through plate |0I and locked in the desired position of adjustment by a nut I44.

- Plate MI is fulcrumed on a line x-x (Fig. 17) connecting the center of a stud I45 with the center of a screw I 50. Stud I45 attached to a bracket I46 (which screws I 46a attach to the partition 32) is surrounded by a spring I41 (Fig. 13) which surrounds a bushing I48 attached to plate IOI. Bushing I48 provides a hemi-spherical socket for receiving the like-shaped end of stud I49 attached to the partition. Spring I 41 urges the plate IOI against the stud I 49. Screw I50 (Fig. 19), attached to a bracket I5I, retains a spring I52 which urges a ball I53 against the 5 plate -.I0.I and the flatter-against a pin I54 par- ;riedpy the bracket 1-51.. 'Braclret .I5:I has slot 455 which receives screws --.I.'5.t which are threaded into the partition. By loosening these screws, the bracket I51 *ca-n he s-hinted horizontally in Fig. .17 to vary the relation of .tulcrum .line :.r--rc to the sleeve valve 184 for a purpose :to be described. .Fig. .13 shows a spring .151 surrounding .a stud 1.5a :mounted in the partition and can tending -through the plate 'I0.I.. This spring I51 urges plate I'I against the'disc I02 of lever M5 wig. .15

Gear 50 drives a gear I150 which drives ta gear pump :IB I retained in a pocket ol? *the partition .32 (Fig. 129 ibyscrews 1.62. The pump has an :inlet 230 connected-with the oll supply within the housing above and below the partition. The pump outlet 23 I is connected with a .fi'lter "pocket 2 3.2 (Figs. 1-4 and containing a rfilter I64 which a'cover 465., secured by screws 1 66 to the housing, retains in the pocket. Oil is filtered as it passes into the interior of the filter which .is connected with ducts 23-4 and 231'! (Figs. .14, .20 and 22.1.9. Duct 23! leads to .a partition pocket .130 I-Eigs.

,13 and 21:) which receives parts :of a pressure regulator including a valve sleeve III :having :a .seal ring all-.2 and a groove I13 which ports I14 connect with the rcylindrical more H5 which :re- .ceives ;a piston valve 416 whose .stem ZI "I51 marries .a disc 41:8 which retains a spring :I EH1. When the pressure in :pocket 11.0 exceeds :a ccertain'walue, valve :I'Ia6 moves down to open ports 1'14 "to -permit oil to escape to the tank -.or Ireservoir prow vided :by the housing. Bracket 146 retains sleeve 1111!.

Referring to Figs. 3-8, a casting I00 attached to housing 3| by screws I8I receives a cylinder 132 secured by screws I 33 surrounding -a piston 184 connected with :a :rod I 85 which actua'tes a blade-pitch setting device not shown). disclosed in the copending application of Muzzey and-Garson, serial No. 19,5714, tiled April 8, 1948, the blade-pitch settin device controls mechanism in the propeller huh which turns the blades to the angles demanded by the setting device. The piston rod end of cylinder [82 is connected with duct 240 which is connected by oppositely opening check valves I90 and 191 (Fig. 23') with a duct 239. The valves I90 and I91 are located in cages I92 and 193 respectively shaving re- 18-0, and are each connected with :a pocket I08 7 in the casting (Figs. 5-8'). Pocket 198 receives a valve guide I39 having ports 200 and'20I connected respectively with ducts 2'40 and 239, said ducts being separated by a seal 202, Guide 1'99 receives a valve 203 which a spring '204 :urges toward a cam 205 provided by 'hulo 206 of lever 20! pivotally supported by a stud I208 attached to plate 21.0 and retained by a'nut 209 When lever 20'I'is in the position shown in Fig. 4, or in the position 2Il'I (dotted lines in Fig. 23),, the valve 203 is in position for connecting ducts .239 and 240 and the check valves 1011, 19] and restrictions 194., I85 are Joy-passed and flow intopr out of the rod end of cylinder .182 is not retarded.

When lever .20? is moved counterclockwise (Fig.

4) or clockwise in Fig. 23 to full-Il-i-ne position202l, the valve 203 (Fig. 5) moves down to' elose the by-pass and restriction of fluid-flow into and-out of the rod end of cylinder I82 is provided. Lever 201 is manually eperated between these positions that the pilot can select either slow or :tast operation of the hiarle pitch setting piston 'I-;B15. Movement of 1ever201 is limited toy a pin 2J2 attached to plate 2510 and engaging a slot 213 in the lever hub 206. The restrictions 194 and I95 can be different in size so that retardation of movement in the .two directions will be different.

Rolex-ring to Figs. 20-23, tank '-I, which represents the oil reservoir in the housing 31 connected by duct 230 with the inlet of pump I6I whose outlet connected by duct 231 with filter pocket 232 whose outlets are connected with ducts 234 and 231. Duct 23 connects with the pressure regulator PR and with duct 233 which 7 connects with duct 239. Duct 2-34 connects with port '88 of valve guide 85 and with duct 235 connected with port I34 of valve guide I 30. Port 86 of valve guide 85 is connected by ducts 1245 and 245a (in cover I20, Fig, 15) with the upper end of stabilizer cylinder III 9. The lower end :of cylinder 1129 is connected by duct 1236 with port I36 of valve I30 and with duct 236a connected with the upper end of cylinder I82.

When there :is no speed :error, valves .1 40, 80

and 4 and stabilizer piston I I8 are in equilibrium "position shown and there is :no movement of servo-piston I84. If there is under-speed error, "va'lve180 moves down and the upperend 10f icylinder 1 I9 receives pressure fluid and piston Ht! moves down and :84 moves down. :Since valve 84 operates as a follow-up, the downward displacements of piston H6 and valve 84 are proportional to the amount of speed error. .As valve -84 moves down, valve I40 moves down and its displacement is proportional to the amount of speed error. The rate of displacement :of piston H8 is proportional to the rate of change of speed error and fluid flows out throughducts 236 and 236a to the top cylinder 182 at a rate proportional to the rate of change of speed error. When valve I40 moves down, duct 236 is-connected with the pump, and fluid flows outport .I 3.6 into duct 236 at a rate proportional to displacement of valve I40 which proportional to speed error. Therefore the combined rate of flow through duct 23611 is in proportion to speed error and to the rate of change of speed error. Rod I85 moves down to effect blade angle decrease at a rate proportional .to speed error and rate of change of speed error. The underspeed error is connected by a stabilized governin action.

When there is overspeed error, the action is .reversed. Upward movement of 'valve is accompanied by upward movements of piston-I I8, valve 84 :and valve I30. The upper end of cylinder H9 .is connected with drain through duct in the lower end of valve 34.; and the upper end of cylinder 48.2 :is connected with drain through port I36 of valve guide I30. As piston H 8 moves up at arate proportional to rate of change of speed error, fluid will flow .from the upper end of cylinder I82 at that rate through ducts 236a and 236 into the lower end of cylinder -I I 9. Since the upward dis-- placement of valve I40 .is proportional to speed erron, fluid will flow .from the upper end of cylinder I'82 through port .136 at a rate proportional to the amount .of speed error. Therefore the combined flow rate from the upper end of the cylinder I82 is in proportion to speed error and the rate of change of speed error, while the piston I84 is moving up under the oil pressure underneath, Therefore .rod I85 moves to effect blade angle increase at a rate proportional to speed error and the ratecf change of speed error.

Although movement of rod I85 is retarded when lever 20! is in the full line position or is not retarded when the lever is at 201', the rate of movement of rod I85 is still proportional to speed error and to the rate of change of speed error. I rate of movement can be represented by km-l-kzh in which n is speed error and n is rate of change of speed error and k1 and R2 are factors which.

can be altered by the adjustments which have I been described. The adjustment of fulcrum I04 by screw I01, known as the acceleration rate adjustment, determines Ice. The adjustment of the fulcrum of lever-plate IOI by bracket I5I, known as the error rate adjustment determines in. By altering these factors, the apparatus can be adjusted to give the required governing action for a particular engine.

Referring to Figs. 15, 16, 17 and 23, a plug 300 received by a hole in housing 3| guides rods SM and 302 urged left (Fig. by springs 303 and 304, respectively (Fig. 17), against levers 305 and 306 pivoted at 30'! and 308 respectively on ears 309 and BIG, respectively, provided by the plug. Levers 305 and 30B are engaged by a rod I I 51- carried by lever H5. In the equilibrium position of rod H1, both switches 3H and SH! are open. When, as result of underspeed, rod II! moves up from equilibrium position, lever 305 is moved clockwise (Fig.15) to push rod 30E right to close normally open switch 3. When, as result'of overspeed, rod ill moves down from equilibrium position, lever 306 moves counterclockwise (Fig. 15) to push rod 302 right to close normally open switch 3I2, The closing of switches 3H and 3I2 (Fig. 17) will effect operation of devices (such as lamps) for indicating underspeed and overspeed, respectively. The switch operating means and not the indicating system as a whole is a part of the present invention.

The present controller is suitable for use with an internal combustion turbine and propeller power plant for airplanes. Power output being a function of the torque and the speed, the output can be varied by control of fuel (not shown) and the speed can be varied by adjusting the governofspring 6I through the lever I2. If, under cruise conditions, increase of power by increase of speed as well as increase of fuel is desired suddenly and the spring 6| is suddenly compressed by lever 12, the valve 80 is suddenly forced down from its equilibrium position with the result that blade angle would be suddenl reduced and then there would be a false or over acceleration. If valve lever 20'! is in position 201 (Fig. 23), the by-pass around the restrictions I94, I95 will be closed so that piston I84 will respond slowly to the demands of the governor, and false acceleration will be substantially reduced. Under full power conditions when quicker response by the governor to correct speed error is required, the by-pass valve lever is moved to position 20! (Fig. 23) so that theby-pass around the restrictions I94, I95 will be open.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Apparatus for controlling blade angle comprising an hydraulio servo having a cylinder, a piston therein and a rod connected with the piston and extending through one end of the cylinder and connectible with blade angle changing mechanism, a fluid reservoir, a pump connected with the reservoir for supplying fluid under pressure, means connecting the pump with the rod end of the servo-cylinder, a fiyweight governor, means for driving the pump and governor, a stabilizer cylinder, a piston therein, a rod extending from the piston through one end of said cylinder, a lever connected with said stabilizer piston rod, a fulcrum for said lever, a duct connecting one end of the stabilizer cylinder with the head end of the servo-cylinder, means for controlling admission of pressure fluid from the pump to the other end of the stabilizer cylinder or the draining thereof and comprising a valve connected with the governor and a follow-up valve operated by the lever, means for controlling admission of pressure fluid from the pump to the head end of servo-cylinder or the draining thereof and comprising a third valve and a second lever operated by the first lever for operating said third valve and a fulcrum for the second lever, a nonrotatable nut supporting the first lever fulcrum, means for adjusting the nut laterally in the direction of movement of the follow-up valve, and a screw for moving the nut axially.

2. Apparatus for controlling blade angle comprising an hydraulic servo having a cylinder, a piston therein and a rod connected with the piston and extending through one end of the cylinder and connectible with blade angle changing mechanism, a fluid reservoir, a pump connected with the'reservoir for supplying fluid under pressure, means connecting the pump with the rod end of the servo-cylinder, a fiyweight governor,

- means for driving the pump and governor, a stabilizer cylinder, a piston therein, a rod extending from the piston through one end of said cylinder, a lever connected with said stabilizer piston rod, a fulcrum for said lever, a duct connecting one end of the stabilizer cylinder with the head end of the servo-cylinder, means for controlling admission of pressure fluid from the pump to the other end of the stabilizer cylinder or the draining. thereof and comprising a valve connected with the governor and a follow-up valve operated by the lever, means for controlling admisend of servo-cylinder or the draining thereof and comprising a third valve and a second lever operated by the first lever for operating said third valve and a fulcrum for the second lever, means for supporting the bushing for rotation on axis transverse to the direction of movement of the follow-up valve, means for securing the bushing in the desired angular position in order to adjust the nut and the first lever fulcrum laterally in the direction of movement of the follow-up valve, means for preventing rotation of the nut and a screw for moving the nut in order to adjust the first lever fulcrum transverse to the direction of movement of the follow-up valve.

3. Apparatus for controlling blade angle comprising an hydraulic servo having a cylinder, a piston therein and a rod connected with the piston and extending through one end of the cylinder and connectible with blade angle changing mechanism, a fluid reservoir, a pump connected with the reservoir for supplying fluid under pressure, means connecting the pump with the rod end of the servo-cylinder, a fiyweight governor, means for driving the pump and governor, a stabilizer cylinder, a piston therein, a rod extending end of the stabilizer cylinder with the head end of the servo-cylinder, means for controlling admission of pressure fluid from the pump to the other end of the stabilizer cylinder or the draining thereof and comprising a valve connected with the governor and a follow-up valve operated by the lever, means for controlling admission of pressure fluid from the pump to the head end of servo-cylinder or the draining thereof and comprising a third valve and a second lever operated by the first lever for operating said third valve and a fulcrum for the second lever, a cylindrical nut supportin the first lever fulcrum, means for preventing rotation of the nut, a rotatable bushing having a hole which receives the nut and which is eccentric to the bushing axis and parallel thereto, a screw having a head by which it is turned in order to move the nut axially, and the first lever fulcrum in a direction transverse to the direction of movement of the follow-up valve, said bushing having a flange which surrounds a recess of the bushing and which receives the head of the screw, a member providing a cylindrical opening in which the bushing is journaled and a recess receiving the flange of the bushing, said opening being on an axis transverse to the direction of movement of the follow up valve, whereby rotation of the bushing in said bearing causes the adjustment of the second lever fulcrum in the direction of movement of the follow up valve and whereby axial movement of the nut eifected by turning the screw causes movement of the first lever fulcrum in a direction transverse to the direction of movement of the follow up valve, means for securing the bushing to the member in a position of adjustment, and a cover attached to the member for retaining the bushing in her and engaging the screw head to clamp it to the bushing in a position of axial adjustment of the screw.

4. Apparatus for controlling blade angle comprising an hydraulic servo having a cylinder, a piston therein, and a rod connected with the piston and extending through one end of the cylinder and connectible with blade angle changing mechanism, a fluid reservoir, a pump connected with the reservoir for supplying fluid under pressure, means connecting the pump with the rod end of the servo-cylinder, a fiyweight governor, means for driving the pump and governor, a stabilizer cylinder, a piston therein, a rod extending from the piston through one end of said cylinder, a lever connected with said stabilizer piston rod, a fulcrum for said lever, a duct connecting one end of the stabilizer cylinder with the head end of the servo-cylinder, means for controlling admission of pressure fluid from the pump to the other end of the stabilizer cylinder or the draining thereof and comprising a valve connected with the governor and a follow-up valve operated by the lever, means for controlling admission of pressure fluid from the pump to the head end of servo-cylinder or the draining thereof and comprising a third valve and a second lever operated by the first lever for operating said valve and a fulcrum for the second lever, electric switches respectively for controlling devices which respectively indicate overspeed and underspeed, and having actuators movable in direction transverse said mem-- to the direction of movement of the stabilizer piston, means for causing movement of one actuator in response to movement of the stabilizer piston in one direction immediately away from equilibrium position and means for causing movement of the other actuator in response to movement of the stabilizer piston in the other direction immediately away from equilibrium position.

5. Apparatus for controlling blade angle comprising am hydraulic servo havin a cylinder, a piston therein, and a rod connected with the piston and extending through one end of the cylinder and connectible with blade angle changing mechanism, a fluid reservoir, a pump connected with the reservoir for supplying fluid under pressure, means connecting the pump with the rod end of the servo-cylinder, a flyweight governor, means for driving the pump and governor, a stabilizer cylinder, a piston therein, a rod extending from the piston through one end of said cylinder, a lever connected with said stabilizer piston rod, a fulcrum for said lever, a duct connecting one end of the stabilizer cylinder with the head end of the servo-cylinder, means for controlling admission of pressure fluid from the pump to the other end of the stabilizer cylinder or the draining thereof and comprising a valve connected with the governor and a follow-up valve operated by the lever, means for controlling admission of pressure fluid from the pump to the head end of servo-cylinder or the draining thereof and comprising a valve and a second lever operated by the first lever for operating said valve and a fulcrum for the second lever, electric switches respectively for controlling devices which respectively indicate overspeed and underspeed and having actuators in a plane transverse to the axis of the stabilizer piston, a member movable with said piston, and two levers respectively engaging the actuators and pivoted on axes respectively on opposite sides of the plane of the actuators, said levers having edge surfaces normally engaged by the member and said edge surfaces having portions oblique to the axis of the stabilizer piston and extending in opposite directions from said member and toward said piston whereby the switch actuators are respectively moved immediately in response to movements of the piston away from equilibrium position.

ROY H. BRANDES.

4 file of this patent:

UNITED STATES PATENTS Number Name Date 1,891,096 Kraft Dec. 13, 1932 1,933,311 Caughey Oct. 31, 1933 1,976,659 Dickinson Oct. 9, 1934 2,197,743 Crafts Apr. 16, 1940 2,299,635 McNeil Oct. 20, 1942 2,328,451 Hedman Aug. 31, 1943 FOREIGN PATENTS Number Country Date 7,548 Australia Apr. 17, 1928 of 1927 

